Why does the 535i use the regular N55 and not the N55HP? The N55HP has about a 15hp plus than the regular N55, along with more torque. Using the regular N55 makes the 535i a tad slower than the 535d, using the N57 (2011-present version). I find this a bit odd... Why make the 535i slower than the 535d?

2) The N55 is supposedly being replaced with the introduction of the 4-Series Coupe. Although the change would be very minor, I could see why they don't want to change it for one model year then change it again to a completely different engine.

The 535d is a different price point and definitely a step ahead on performance. BMW numbering is where I see the issue. 530i is nearly £3,500 cheaper than 530d and is lower on performance. 535i ought to be the 530i, IMO, and a more powerful petrol engine for the 535i. After all there is almost £3,750 to play with, even when you add the auto to get to 535d spec'. At present BMW seem to be sitting the 5-series petrol models in between the diesels, not as direct comparisons.

535i will get an update with the facelift and will gain considerably (+10% torque). The 535d has massive torque already, you have to compare with a V8 gasoline engine. It's very comparable to the 550i to that respect.

Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."